The invention pertains to lock-operating mechanism specifically applicable to the door or doors of a jail cell, wherein the door or doors are horizontally displaceable, for selectively opening and closing an individual cell door from a remote-control station, and wherein an emergency release bar is independently actuable to open all doors for a given plurality of cells, in the event of a fire or other life-threatening emergency.
U.S. Pat. No. 3,426,478 discloses an illustrative jail-cell door-locking system of the general character indicated, wherein a housing is located above each cell door, in a horizontally distributed succesion of individual cells, as along a corridor. A reversible rack-and-pinion drive means is within each housing for horizontally moving the involved door (via its suspension carriage) between open and closed positions. A horizontally movable emergency release bar extends from the remote-control station and through each of the housings. A vertical locking column is adjacent each door opening, and a locking head is vertically movable within the locking column. Bolt means in each vertical column is fixed to the locking head and engageable with the involved door to hold the door in its closed position. A pivotal deadlock device is provided to prevent vertical movement of the locking head, to thereby prevent unlocking the bolt means. Cam actuator means on the release bar pivots the deadlock device out of deadlocking position and shifts the locking head to unlock all cell doors when the release bar is moved axially. A lost-motion connection between the rack and the carriage permits some motor-driven rack displacement for locking/unlocking purposes, before the driven rack drives the carriage and its suspended door. The drive motor and its rack pinion are carried by a hinged frame that is cam lifted away from rack engagement when the mechanism has fully locked and deadlocked the door in closed position.
Another prior-art mechanism utilizes an endless sprocket-chain drive from a frame-mounted motor to the carriage from which the cell door is suspended, with a lost-motion connection between the sprocket chain and the carriage, whereby the lost-motion connection affords opportunity to release locking-bolt and deadlock devices prior to having the sprocket chain displace the carriage in door-opening and door-closing phases of an overall cycle of operation.
But the mechanism of said patent and of the endless-chain arrangement suffer from the problem of affording inadequate human safety unless additional measures, such as a slip-clutch, are provided in the motor drive to the spur gear (for the rack-and-pinion drive) or to the drive sprocket (for the sprocket-chain arrangement). In both situations, there is added complexity in any such provision, and the inertial factors in other elements of the involved overall system of releasing associated locking-bolt and deadlock mechanisms are greater than I have found to be necessary. As a result, the power-capacity requirements for the reversible electric-motor drive have been greater than I now find to be necessary.